Braun tube



April 23,.1936- .M. VON ARDENNE} 2,039,132

BRAUN TUBE Filed June 14, 1932 FAG. 2

J'nuenfor:

wardly curved Patented Apr. 28, 1936 PATENT, OFFICE BRAUN TUBE Manfredvon Ardenne, Berlin, to Radioaktiengesellachai't Germany, assignor D. S.Lowe, Berlin- Steglltz, Germany, a company of Germany Application June14, 1932, Serial No.

In Germany June 19, 1931 6 Claims. (01. 250-275) The subject matter ofthis invention is constitutedby a Braun tube, which is distinguished bythe fact that the same, whilst of extremely simple construction, permitsof the formation of light-intensive, undistorted images of the lightimages produced by the cathode ray. According to the invention, thebottom of the Braun tube bearing the fluorescent screen is, incontradlstinction to the tubes heretofore known, constructed with acurvature towards the inside, whereby on the one hand the strength ofthe bottom of thebulb is considerably increased (in the case of Brauntubes furnished with an outbottom a very large number of rejections areto be expected, owing to a'pressing in of the bottom due to the largesurface and the low internal pressure), whilst on the other hand for thepurpose of projection of the fluorescent effect on to a relatively largescreen lenses may form of embodiment.

be employed, which require no correction, or merely a very slight one,to obtain a flat repre- 'sentation of the image produced on the cup-likefluorescent layer.

This projection' valve may be furnished with a structural system thatthe valve may be employed, notonly for the purpose of scientificresearch, but also for quite cheap television arrangements.

. In order to obtain the least possible distortion of image and toenable and accordingly cheaper lenses to'be employed, the valve, andmore particularly, therefore, the bottom thereof, is constructed assmall as possible, which at the same time results in an increasedstrength of the valve. The size of the requisite screen is limited onlyby the permissible heating of the fluorescent material. -As my testshave been showing, it is possible without particular difliculty toobtain sizes of image amounting to approximately 10 sq..cm.,toimagesofthesizeof3x3upto3x4cm., whereby it is quite possible, by meansof suitable lenses, to obtain avlinear light-intensive enlargement ofthe amount. a

The invention is describedv more particularly in the following inconjunctionwlth a possible In Fig. 1, l designates the wall of thevalve, which is preferably constructed as a cylindrical tube, and 2 theinwardly curved bottom bearing on its inner side the fluorescent layer3. .In order to obtain the least possible distortion of theimasethevalve is made as short as possible, for example 20 cm., in length,and possesses a diameter of 4.5-6 cm, The radius which 'is so extremelysimple the smallest possiblethe short life of the corresponding age upto 10-15 times the of curvature of the depression or focal radius of thelens employed is, in accordance with the additional subject matter ofthe application, so chosen that the curvature of the depression issomewhat larger than corresponds with the focal radius of the lens. Theuse of lenses is thus rendered possible, which preclude distortion ofthe marginal image without aplanatic correction.

In accordance with the additional subject matter of the invention, thesingle system parts of the Braun tube are provided on a, common glasssupport, whereby, prior to the fixture in the glass bulb, the requisiteaccuracy in'the relative position of the single elements may be soexactly determined mechanically as to conform to the requirements placedthereon by an appreciable enlargement. This glass support is designated4 in Fig. -1. The same possesses at the centre the cathode 5, theWehnelt cylinder 6, the anode .1

and the pairs of deflecting plates 8 and 9. mac

order to prevent a flashing over, which might readily occur in view ofthe compact construction as a result of the common support, the supporting wires or metallic supporting parts are screened off against eachother by means of glass tubes, so that the lines of discharge areconsiderably increased. The complete valve may now be mounted lirasocket l0 possessing-the requisite number of contacts, as employed, for

example, in the case of the known multi-stage valves.

In valves of this nature, as employed, therefore, more particularly forpurposes of television, cathode heretofore has been found verydisturbing; This is due more particularly to the fact that the cathode,by reason of impinging ions, isvery rapidly destroyed. To prevent thisthe surface of the Wehnelt cylinder is, in accordance with theinvention, very considerably increased, or the cathode suflicientlyscreened off by shutters disposed in front of the same. By means of thisshutters, which preferably are constructed in the form of circular orrectangular perforated bands, there is also obtained at the same time a.good concentration such as cannot be dispensed with in connection withthe great intensity of light required for-the projection. The valveillustrated in Fig. 1 is furnished with a perforated shutter ll of thisdescription. Y I v I The second possibility above referred to ofappreciably increasing the durability by increasing the surface of theWehnelt cylinder is illustrated in Fig.2. In this figure 5 is thecathode,,6

the Wehnelt cylinder, and I4 a metallicscreen additionally increasingthe protection offered to the cathode. An arrangement of this kind isindicated in Fig. 2 in dotted lines. In the possible forms of embodimentof the Braun tube as described there is preferably employed a cathode,which consists of anelectron-emissive cup preferably heated in indirectfashion by means of a spiral. In a cathode construction of this naturethere is obtained an extremely concentrated, strong ionic source, suchas absolutely essential for producing the requisite small but brilliantcross-section of the beam. To obtain an effectiveness as faultless aspossible as' regards the valve according to the invention it ispreferable to employ as filling for the discharge space amixture ofnoble gases. It is also of advantage to screen off the valve towards theexterior, for example by means of a silver mirror applied to the insideor the outside of the wall of the valve. Further, it is of advantage, in7 order to prevent disturbing charges of the fluorescent screen, to makethe latter conductive, for example by an addition of metallic powder. Toobtain the requisite intensity of the beam there is preferably employedan anode potential amounting to 4000-10000 volts.

The projection valve according to the invention may be mounted in simplefashion, as illustrated in Fig. 1, together with a lens l2, and theimage thus produced'projected on to a screen l3 disposed at a remotepoint. It is, however, also possible, if the apparatus is to be locatedwithin a small space, for instance in a loud speaker, to fit in thevalve insuch fashion that the same is 0 arranged vertically to the axisof the diaphragm,

Iand projects the image, through the medium of a flat mirror, in adirection in or parallel to the axis of the diaphragm, where the same,through the medium of the optic, appears ona transparent screen arrangedin front of the diaphragm. An arrangement of this kind is illustrated inFig. 3. In the latter i5 is the valve, .which is seated in the mountingl6 and, by means of an orifice in the conical member i1, performsradiation on to a flat mirror [8 which, throughthe medium of the lens[9, causes the image to be produced on the screen 20. 2| is theloud-speaker system; which, for example, may be constructed in the,formofa dynamic loud speaker. I

I claim: 1. In an arrangement for producing pictures, preferably fortelevision purposes, a Braun tube having a hot cathode,-an anode, afluorescent screen on the bottom of'said tube, means to control andmeans to deflect the cathode ray to produce images on said fluorescentscreen; and a lens for projecting said images on to a projection screenfor obtaining an enlarged copy of said light image, the bottom ofsaidBraun tube being depressed, the focal radius of said lens being just aslarge as or somewhat larger than the radius of the curvature of thedepression of the bottom of said Braun tube.

2. In an arrangement for producing'pictures, preferably for televisionpurposes, a Braun tube a fluorescent screen on the bottom oflsaid tube,means to control and means to deflect the cathode ray to pro;

duce images on said fluorescent screen, said screen possessing a usefulrectangular area of not appreciably more than 12 square centimetres; and

preferably for television purposes, a Braun tube of a very short lengthin the order of about 20 centimetres, said Braun tube, having a hotcathode, an anode, a fluorescent screen on the bottom of said'tube,means to control and means to deflect the cathode ray to produce imageson said fluorescent screen; and a lens for projecting said images onto aprojection screen for obtaining an enlarged copy of said light image,the bottom of said Braun tube being depressed, the focal radius of saidlens being just as large as or somewhat larger than the radius of-thecurvature of the depression of the bottom of said Braun tube.

4. In an arrangement for producing pictures, preferably for televisionpurposes, a Braun tube having a hot cathode; an anode; a Wehneltcylinder, the surface of which isrincreased by metallic parts notrequired for the purpose of concentration, preferably by means ofcircular plate abutments; a fluorescent screen on the bottom of saidtube; means to control and means to deflect the cathode ray to produceimages on said fluorescent screen; and a lens for projecting said imagesonto a projection screen for obtaining an enlarged copy of said lightimage; the bottom of said Braun tube being depressed, the focal radiusof said lens being just as large as or somewhat pression ofthe bottom ofsaid Braun tube.

5. In an. arrangement for producing pictures, preferably for televisionpurposes, a Braun tube including a Wehnelt cylinder; a cathode mountedinside said Wehnelt cylinder; a perforated shutter with preferablycircular or rectangular perforation to screen off said cathode, saidshutter being preferably connected with said Wehnelt cylinder; an anode;a fluorescent screen on the bottom of said Braun tube; means to controland means to deflect the cathode ray to produce images on saidfluorescent screen; and a lens for projecting said images onto aprojection screen for obtaining an enlarged copy of said light image;the bottomwof said Braun tube being depressed; the focal radius of saidlens being just as large as or somewhat larger than the radius Y of saidBrauntube.

'6. In an arrangement for producing pictures, preferably for televisionpurposes, a Braun tube having its discharge space fllled with a mixtureof noble gases and including a hot cathode; an anode; a fluorescentscreen on the bottom of said tube; means to control and means to deflectthe cathode ray to produce images on said fluorescent screen; and a lensfor projecting said images onto .a projection screen for obtaining anenlarged copy of said light image; the bottom of said Braun tube beingdepressed; the focal radius of said lens being just as large as orsomewhat larger than the radius of the curvature of the depression ofthe bottom of said Braun tube.

MANFRED VON ARDENNE.

